Method and apparatus for operating a multiple hearth furnace
OwnerLouis T. Barry, Mark B. McCormickinventors
Life of this patent
Estimating the term…
Abstract
A multiple hearth furnace having a drying zone, a combustion zone and a cooling zone includes a recirculation loop that recycles exhaust gas from the drying zone to the cooling zone. In some embodiments, a first control loop including a temperature measurement device that measures temperature in the combustion zone controls fan speed of a recirculation fan that drives the recirculation loop. A second control loop monitors recirculation fan temperature and overrides the first control loop if the recirculation fan temperature exceeds a predetermined maximum. A third control loop controls air flow into the furnace.
Claims14
A multiple hearth furnace comprising:
- a plurality of hearths arranged in superposed relation,
- at least a first of said hearths defining a drying zone,
- at least a second of said hearths defining a combustion zone, and
- at least a third of said hearths defining a cooling zone, wherein:
- said drying zone is operable to dry material to be combusted;
- said combustion zone is disposed beneath said drying zone and is operable to combust dried material received from said drying zone;
- said cooling zone is disposed beneath said combustion zone and is operable to cool combusted material received from said combustion zone;
- means for transferring said material sequentially from said first hearth defining said drying zone to said second hearth defining said combustion zone to said third hearth defining said cooling zone;
- means for recirculating gases from the drying zone to the cooling zone.
A multiple hearth furnace comprising:
- a plurality of hearths, organized into at least first, second, and third superposed zones, for incinerating material that passes sequentially through said zones;
- means for measuring a parameter present in said second zone;
- and
- means for adjusting feedback of flue gases between said first and said third zones based upon said parameter measure in said second zone.
Apparatus for controlling a multiple hearth furnace wherein the hearths are divided into a plurality of zones, said apparatus comprising:
- a recirculation path for moving gas between a first zone and a second zone of said multiple hearth furnace;
- adjustable valve means for allowing an adjustable amount of air from external to said multiple hearth furnace to be mixed with gas being recirculated from said first zone to said second zone;
- and
- means for adjusting said valve means in response to a first parameter within at least one of said zones and a second parameter external to said multiple hearth furnace.
Apparatus for controlling a multiple hearth furnace, said multiple hearths arranged in superposed relation and defining a first zone that overlies a second zone that overlies a third zone, comprising:
- means for recirculating flue gases from said first zone to said third zone;
- control electronics for controlling said means for recirculating flue gases, wherein:
- said control electronics control said means responsive to a temperature of said second zone when a first temperature of said means is below a predetermined value, and
- said control electronics control said means responsive to said first temperature when said first temperature equals or exceeds said predetermined value.
Dependencies are inferred from the claim text.